Thermal cut-out for electrical circuits.



H. A. & W. H. HOESCHEN.

THERMAL CUT-OUT FOR ELECTRICAL CIRCUITS.

APPLLCATION FILED MAR. 21. 1917.

1 278,467 I Patented Sept. 10, 1918.

HLAHO es 0 /7 e n, 51M ue M 910,

I/JZFmHHOes ch en, QM l nens:

alarm when it operates to open the circuit, 20

I I UNITED STATES, PATENT or-ricn.

HENRYSA. HOESCHEN AND WILLIAM HOE SCHEN, OF OMAHA, NEBRASKA, ASSIGNORS TO BAKERICE MACHINE COMPANY, OF OMAHA, NEBRASKA, A CORPORATION OF Y nnrmsxe.

THERMAL CUT-OUT FOR ELECTRICAL CIRCUITS.

Specification of Letters Il'atent. Patented Sept. 10, 1918.

Application filed March 21, 1917. Serial No. 156,423.

and WILLIAM HQHOESCHEN, citizens of the- United States, and residents of Omaha, in the county of Douglas and State of Ne- 'braska, have invented certain new and useful Improvements in Thermal Cut-Outs for ElectricalOircuits, of which the following is a specification. I Our invention relates .to devices for automatically opening an electrical circuit when the current in the circuit exceeds a predetermined maximum and is maintained for a suflicient time to cause heating of a conductor forming a part of the circuit. It is the object of our invention to provide a simple and inexpensively constructed device of this kind, provided with means for causing an and which may be readily restored to operative .condition without replacement of any of its members. A further object of our 7 invention is to provide in a device of this 26 ing ot er than the flow of current in the circuit,

class means for automatically compensatfor temperature changes caused by means so that the thermal expansion causing the cut-out operation will be substantially independent of atmospheric temperatures.

In the accompanyin drawings, Figure 1 is a front view of a dievice embodying our invention, Fig. 2 is aside view of the same, Fig. 3 is a detailvertical section on the plane of the line 33 of Fig. 1, and Fig. 4 is a detail horizontal section on the plane .of the line 4-4 of Fig. 1.

In the illustrated embodiment of our invention we rovide a cylindrical of tubular member 5 w ich is held in a fixed, preferably vertical, position by means of a supporting bracket connected therewith intermediate its ends. Said bracket comprises a base portion 6 which is attached to a suitable sup--,

gOthel 'by clamp-bolts 9* extending trans- 'v ersely through them as shown. Near the per end of the mem r 5 there is a clamp- 10, similar to the annular portion 7 of 59, supporting bracket, said ring having at h'' front side thereof lugs 11 which are drawn toward each other by a clamp-bolt 12 screws 31.

to close the ring upon the tubular member. A ring or sleeve 13 of insulating material is placed around the member 5 within the ring 10, so that the latter is electrically separated from the I former. A ring 14 is clamped on to the member 5 near the lower end thereof. Another ring 15 is clamped thereon slightly below the ring 10, and a. pair of rings 16 and 17 are clamped thereon below the bracket-ring 7,v all of said rings having insulating sleeves 13 between the same and the supporting tube 5, and being clamped similarly to the ring 10. The ring 14 has an integral laterally extending lug or arm 18 which is terminally forked and curved downwardly into a plane beneath theend of the tube 5. A latch-bar 19 is pivoted on a pin 20 between the forked terminals of said arm 18, said bar 19 extending across beneath the end of the tube and being movable in a vertical plane. In the lower end of the tube 5 there is a plug or socket 21 of insulating material, having therein a cylindrical recess in which is held a coil. spring 22, the lower end of said spring engaging the latch-bar 19 to yieldably press thesame downwardly. The latch-bar is held in a substantially horizontal position by means ofa rod or-wire 23 of electrically conductive and thermally expansible mate- .rial,the lower end of the wire extending through an opening in the bar near the pivoted end thereof and having an integral enlar ed portion or button 24 fitting in a recess t erefor -in the lower side of the bar. The upper end of the wire 23 has an integral upset ,or enlarged threaded portion 25 which passes slidably through a vertical opening in 3. lug 26 extending laterally from the clamp-ring 10, and said threaded head-portion is held in adjusted relations to said lug by means of nuts 27 and 28 screwed thereon above and below the lug, as shown. Extending laterally from the clamp-ring 15, and integral therewith, is a head'29 having a fiat vertlcal outer face to which the upper end of a fiat spring 30 is secured by means of Said spring 30 is formed or biased so as to tend to assume the curvilinear form indicated by dotted lines in"Fig. 1. The lower'end "of said spring is normally on aged by a hook or shoulder 32 near the end of the latch-bar 19' and the spring is thereby held in the rectilinear form shown by full lines in the drawing. Near said lower end of the spring 30 there is secured on the inner side thereof a U-shaped contactplate 33 of which the sides are kerfed to posts 35 and 36, or other suitable means for connection with the terminals M of an electrical circuit, so that the same will be completedthrouglr the parts 30, 33, 31-, 19, 23, 25, 26 and 10, when the'spring 30 is in its normal or engaged relation to the latch=bar 19. It may be noted that, besides the principal electrical connection between the spring 30 and the latch-bar 19, afforded by the parts 33 and 34, the spring alsodirectly enages and is in electrical connection with t e shoulder 32 of the bar. The parts 5, 23 and 30 are preferably made of metals having the same or substantially the same coefficient of thermal expansion, and the spring 30 is so proportioned as to have considerably greater-electrical conductivity than the wire or rod 23.

In consequence of the described construction, arrangement and proportioning of the parts, when the-device is in use in an-electrical circuit passing through thesame as described, and the amount of current flowing in the circuit is great enough and is continued for a sufiicient time to cause heating and a resultant predeterminable expansion of the member 23, the latch-bar 19 is lowered sufliciently to release the spring 30 from the hook or shoulder 32. Thereupon said spring rapidly assumes the curvilinear form to which it is biased, and disengages the resilient fingers of the contact-plate 33 from the pin 34, thus opening the circuit at this point. Ordinary or atmospheric changes of temperature of the mechanism will have no appreciable effect thereon, since the length of the members 5, 23 and 30 is so nearly the same that there will be no material variations in their relative lengths due to such changes of temperatue.

Simple and convenient means for indicat ing, at a distance therefrom, the operation of the cut-out mechanism, are provided as follows: On the clamp-rings 16 and 17 are integral laterally extending arms 37 and 38 which pass behind the rear edge of the spring 30 and have terminal portions which extend forward laterally of said spring. To said terminal arm-portions are secured resilient contact-plates or springs 39 and 40, of which the first carries, near the end thereof on the side adjacent to the spring 30, a button 41 of insulating material, which said spring 30 engages in assuming the curvilinear form thereof. The spring contact 39 is thereby pushed outward sufliciently to engage the inturned end-portion n the head 29 and the side I of the plate 40 and form electrical connection therewith. The arms 37 and 38 carry binding-posts 42 for connection with wires 43 extending to and forming a circuit through a suitable battery or electrical source 44 and a signal device such as a bell 45. It will be seen that upon operation of the cut-out device to open the main circuit, the signal-circuit will be closed to operate the bell or like device.

Under ordinary conditions, after the main circuit is opened and the flow of current through the wire 23 ceases, the wire will quickly cool to atmospheric temperature, simultaneously contracting to its normal length and restoring the latch-bar to position for engaging the spring 30. Then, if the conditions which caused the overloading of the circuit have been remedied, the cutout may be manually restored to its normal circuit-closing position, by reengaging the spring 30 with the latch-bar, the spring being momentarily bowed intermediate its ends sufiiciently to enable the lower end to pass in over the hook or shoulder 32.

In the event that the cut-out is to be used in amain circuit carrying 'normally a relatively large current, so that the wire 23 may be of such size as to have considerable r1-' gidity without the conductivity thereof being-so great as 'to prevent its heating by an overload of the circuit, the sprin 22 need .rnotbe used, and the expansion 0 the wire 'may be employed directly to actuate the latch-bar to release position. [Said s ring 22 is, of course, used whenever the thic es of the member 23 is so small in proportion to its length that it is incapable of exerting a thrust upon the latch-bar.

Now, having described our invention, what we claim and desire to secure by Letters Patent is:

1. An overload cut-out for electrical circuits, com rising an expansible tubular support, a p uralityof clamp-rings disposed thereon and insulated therefrom, a circuitbreaking device biased-to open-circuit position and carried by saidclamp-rings, means mounted on one of the'clamp-rings atone expansion, a thermally expansible conductor of like material and length extending longiferences of longitudinal expansion of the tudinally of said support; insulating c0n-- same and the support, and a circuit-breaknecting' means between said conductor and ing device connected in a circuit with the 10 support at one end thereof, a latch-bar pivexpansible conductor and normally held by 5 otally connected with the support at the 0 the latch-bar in closed-circuit osition. posit'e end thereof and connected -with the HENRY A. HOE CHEN. conductor to move in accordance withdif- WILLIAM H. HOESOHEN. 

